Quote from Mr. Pinkus...the episodes, according to Valve, are technically HL3.
Which is stupid because each episode only added a few things other than new levels.
A game doesn't have to have new technology to be a sequel. It's the PLOT that defines that. If it were the technology that gave sequel status, then a prequel would have to have lesser technology, which obviously isn't the case.
Oh well though, because they've stated HL isn't stopping at just a trilogy.
They say the episodes are technically HL3 because they are technically a third installment, but that doesn't mean that they won't make a title called "Half-Life 3" and will skip straight to "Half-Life 4". In fact, sicne the episodes were labeled "Half-Life 2: Episode BLANK", it would confuse the mainstream market.
The question isn't whether the episodes count as the third installment, it's whether they will make another installment TITLED Half-Life 3.
Based on the example set by the transition between HL1 and HL2, they'll surely have a completely new setting, a new cast of characters, and a new twist on gameplay.
Now, back to HL2:EP3.
I think my biggest question is this: How will the 360 version be released? It would make sense to release it as either an expansion to The Orange Box or a Live download, but seeing as they are planning the release of Portal 2 as well, what I expect is quite straightforward: another "Orange Box", perhaps with the obvious title "The Orange Box Two", or maybe a more sideways-stepped title, like "The Yellow Box" or "The Fuchsia Box."
Since it would be a disservice to fans to release it with only 2 games (Portal 2 and HL2:EP3), they will likely have a total of 5 games on the discm, just as with Orange Box. They only have 2 known games in development, however, so it's quite possible that they may suprise everyone with some hidden projects.
I'd wager they'd use the same formula as with the first Orange Box, releasing A)A full installment
B)One episode
C)Another episode
D)A Portal installment
E)an online game. B and C are impossible, since they only have one Episode left (Ep3), but they may have something else in store to fill the void.
What I hope for is this as the lineup:
A)Half-Life Source or Black Mesa Source (Preferably BMS, since HLS was pretty half-assed) as the full iInstallment
B)HL2:EP3 as the HL2 episode
C)Possibly some HL2 spin off, like how HL1 had Blue Shift
D)Portal 2 for the Portal installment
E)Day of Defeat Source or Counter Strike Source as the online game